The present invention relates to a load/unload mechanism that reduces dust for a magnetic disk drive.
A head slider included in a magnetic disk drive is caused to fly over the surface of a magnetic disk by the pressure of air currents produced by the rotating magnetic disk acting on its air bearing surface. A rotary actuator rotatably supporting the head slider carries the head slider in a direction substantially parallel to the radius of the magnetic disk to locate the head slider at a position corresponding to a predetermined track. Most magnetic disk drives employ a load/unload mechanism for retracting the head slider to a home position while the magnetic disk drives are stopping or while a recording or a reproducing operation is interrupted.
The load/unload mechanism includes, as principal components, a ramp, a head gimbal assembly (hereinafter, abbreviated to “HGA”) and a magnetic disk. The ramp has a slide surface on which a lifting tab formed at the tip of the HGA slides. The slide surface extends inside the peripheral side surface of the magnetic disk so as to cover a recording surface. A magnetic disk drive for a portable device, such as a notebook-size personal computer or a music reproducing device, has been progressively miniaturized and the thickness of the magnetic disk drive has been progressively reduced. Consequently, the gap between the recording surface of the magnetic disk and the ramp has been progressively diminished.
In some cases the magnetic disk collides against the ramp due to play in a spindle holding mechanism or due to the flexion of the magnetic disk when external shocks or external vibrations are exerted on the magnetic disk drive. It is possible that the magnetic disk collides against the ramp due to the fluttering, namely, an undulating motion, of the magnetic disk caused by air currents produced in the magnetic disk drive by the rotating magnetic disk.
If the magnetic disk collides against or comes into contact with the ramp, the surface of the magnetic disk is scratched or the ramp is damaged and, consequently, particles may be produced. Therefore some measures must be taken to prevent collision or contact between the magnetic disk and the ramp. A ramp structure disclosed in Patent document 1 (Japanese Patent Laid-Open No. 2002-279744) prevents collision between the magnetic disk and the ramp when an external shock is exerted on the magnetic disk drive. In the ramp structure shown in FIG. 1 of Patent document 1, a step is formed between counter surfaces 20B and 20C to prevent damaging a load/unload area 10B of the magnetic disk or forming projections in the load/unload area 10B by the contact of the magnetic disk with the ramp. This structure prevents the collision of the load/unload area of the magnetic disk with the ramp by bringing the circumference of the magnetic disk into contact with the counter surface 20C when an external shock is exerted on the magnetic disk drive.
In a ramp structure shown in FIG. 6 of Patent document 2 (Japanese Patent Laid-Open No. 2001-14820), a surface of a base part 70 of a ramp 60 closely opposed to peripheral parts of magnetic disks 16a and 16b is provided with a chamfered projection 72. The peripheral parts of the magnetic disks are able to come into contact with the projection 72 of the ramp when the magnetic disks are caused to vibrate due to exertion of shocks on the HDD (hard disk drive). Consequently, the recording surfaces of the magnetic disks and the surface of the ramp are protected from damaging actions.
In the inventions disclosed in the foregoing documents, the object of preventing collision between the ramp and the magnetic disk is to protect the magnetic disk. Therefore, the peripheral part of the magnetic disk is permitted to come into contact with the ramp. This ramp is one of the sources of particles that will be produced in a magnetic disk drive after the start of using the magnetic disk drive. The inventors of the present invention observed the counter surface of a ramp structure opposed to a magnetic disk to find parts that produce particles in a ramp structure and found that large tool marks are formed in the depth of the counter surface. Contact marks formed by contact between the magnetic disk and the ramp of the magnetic disk drive were found in the circumference of the magnetic disk.
The tool marks were formed in a part of the counter surface of the ramp with which the circumference of the magnetic disk collides. It is inferred that the peripheral edge of the magnetic disk acts like a cutting edge and produces particles by chipping the counter surface of the ramp when the magnetic disk collides against the ramp due to exertion of external vibrations on the operating magnetic disk drive. A magnetic disk drive included in a portable device is highly possible to collide against the ramp particularly while the magnetic disk is rotating.
The foregoing prior art intends to prevent contact between the recording surface of the magnetic disk and the counter surface of the ramp. The circumferential edge of the magnetic disk is brought into contact with the ramp to protect the magnetic disk. Consequently, the production of particles due to contact or collision between the magnetic disk and the ramp, particularly the production of particles due to collision between the rotating magnetic disk and the ramp while the magnetic disk is rotating, cannot be satisfactorily controlled.